Slag Glass Chunk Rock

Discussion in 'Pottery, Glass, and Porcelain' started by Ezlisting, Jun 25, 2014.

  1. Ezlisting

    Ezlisting Member

    I'm thinking this is Slag Glass but my gem tester is registering in the tourmaline/iolite section. Could it be that this piece is so dense that it's throwing off the tester? It weighs 11 pounds; 10 x 4 x 5-inches. The slag glass that I see on ebay are mostly clear, this one is opaque. I'm leaning towards slag glass since tourmaline should have vertical striations, right?


  2. George Nesmith

    George Nesmith Well-Known Member

    Slag glass is typically 2 or more colors swirled together. If this is glass I could be from cleaning out a pot or??? I do not know anything about the rock hound stuff. I does not look like the quartz or crystal I have handled.
  3. Ezlisting

    Ezlisting Member

    Thanks for looking George. It's kind of a mystery to me, too. It's very sharp, but I've hounded crystals and they can be just as sharp as glass. Let's see what others think!
  4. George Nesmith

    George Nesmith Well-Known Member

    Having made radio crystals I know.
  5. clutteredcloset49

    clutteredcloset49 Well-Known Member

    Brasso is a much better tool for determining real vs fake than a gem tester.
    Gem testers are known unreliables, where Brasso continues to prove its worth over and over.

    LOL - couldn't resist.
  6. Ezlisting

    Ezlisting Member

    Too Funny! Where's the idiot now? I've been in Iowa for the last 2 1/2 weeks.
  7. verybrad

    verybrad Well-Known Member

    Looks like glass to me. I used to buy the big chunks of glass in West Virginia and KY at roadside shops to bring North to sell. A lot of it was single color like this and I assumed it was left-overs from the glass houses.
  8. elarnia

    elarnia SIWL

    Probably slag glass but if you want some fun (in terms of what people will argue over and how heated it can get) do a bit of searching on "green obsidian" :) who needs politics to fight over?
  9. gregsglass

    gregsglass Well-Known Member

    I used to buy big blocks like these to decorate my gardens. I was always told that when the big melt pot was being changed or repaired, it would cool down. The interior was one huge block and it would be hammered into hunks for disposal. I always wanted a big hunk of canary or vaseline glass, never got one.
    Boo hoo.
  10. say_it_slowly

    say_it_slowly The worst prison is a closed heart

    If you put your gem tester on another thick hunk of what you know to be glass does it have a similar reading? As I recall glass this color gets it's color from the impurities in it such as iron so any chance it might be caused by impurities. (I have no idea) Does it have little bubbles like some glass?

    Not knowing anything about tourmaline/iolite I did a quick Google and really some rough stones being sold as that are not dissimilar to yours.

    As a kid we visited lots of the WV glass factories and even a marble factory. We also dragged home some large chunks of glass, some a single color, some mixed. They all were a lot sharper than this piece which looks like it could be water worn.
  11. Ezlisting

    Ezlisting Member

    Thanks everyone! I'm going to go with glass. It does have tiny bubbles which should be the deciding factor as I can't think of any rock that has tiny air bubbles. I will get it listed on eBay today.
  12. evelyb30

    evelyb30 Well-Known Member

    Some have bubbles of liquid inside, but not air bubbles that I know of. The fracture patterns on that look like glass to me too.
  13. Cherryhill

    Cherryhill Well-Known Member

    Some slag is formed (glasslike) in the processing of iron ore into iron or steel, this appears to be a piece of that material. It's fused limestone and other stuff. Not really glass at all. It does have conchoidal fracture, as this exhibits.
  14. Ezlisting

    Ezlisting Member

    Cherryhill, thanks for your input. So I should sell it with "slag" in the title?
  15. George Nesmith

    George Nesmith Well-Known Member

    Slag is fine as long as you do not call it glass LOL. something like "Slag chunk from the processing of iron ore" would work.
  16. Ezlisting

    Ezlisting Member

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